A steering device transmits a motion of a steering shaft rotated by an operation of a handle to a pinion shaft as an input shaft of a steering gear. A direction of a wheel is changed by the transmitted motion of the steering gear. In general, the rotary axis of the steering shaft and the axis of the pinion shaft may not be coaxially present. Therefore, an intermediate shaft is provided between the steering shaft and the steering gear through a universal joint, and the end of the intermediate shaft and the steering shaft are coupled to each other. Further, the end of the intermediate shaft and the end of the pinion shaft are coupled to each other through a universal joint. Due to the presence of two universal joints and the intermediate shaft, power transmission is carried out between the steering shaft and the input shaft of the steering gear which are not present on the same straight line with each other.
The intermediate shaft is disposed in a three-dimensional space between the steering shaft and the pinion shaft. In order to equalize the rotational angular velocity of the steering shaft with the rotational angular velocity of the pinion shaft, it is necessary that an intermediate shaft module be disposed so that the angle formed between the rotary axis of the steering shaft and the rotary axis of the intermediate shaft is equal to the angle formed between the axis of the steering gear and the rotary axis of the intermediate shaft. Further, in recent years, the steering device that steers the wheel of the vehicle has been designed by utilizing a simulation technique. For example, there are known techniques disclosed in Patent Literatures 1 to 3.